The linear range of modern turbine flowmeters, usually considered to .+-. 0.5%, is often quite limited and is seldom better than 10 to 1 in dynamic range for a wide range of viscosities. If the turbine meter is calibrated to several viscosities, a family of curves can be plotted, essentially as shown in FIG. 2. The responses indicated are repeatable and the flowmeter range can be extended as much as 100 to 1. However, this does require reference to correction tables or graphs to accurately determine flow.
The family of curves can be reduced to a plot of K, or cycles per gallon, versus frequency, divided by the viscosity as in FIG. 3. The obvious disadvantage, the need to refer to graphs, remains in the present techology if flowmeters are used, over wide ranges of viscosities.
Applicant has devised a method of correcting the non-linearity of flow meters and has extended their usable range by as much as 100 to 1.